Numerous devices have been proposed which are designed and intended to connect various components into functional electronic circuits. Of particular importance here are electrical connectors which are specifically engineered to join printed circuit boards together. It is not surprising that as electrical circuits have become more complicated and sophisticated, the connectors which join various components of these circuits have also become more complicated and sophisticated. Unfortunately, however, it has happened that although the circuitry on printed circuit boards can be effectively miniaturized using state-of-the-art technology, connector technology has not kept pace. This is so for several reasons. First, there are problems with proper registry of the connector with the various circuits on the printed circuit board. Second, there is the ever present problem of establishing and maintaining a reliable and robust electrical contact.
As for the registration problem, several connectors have been disclosed which are engineered with the intent of providing accurate alignment and positioning of the connector contact with the appropriate circuits. It will be easily appreciated, however, that as the particular circuits are made smaller and smaller, the ability to properly and accurately register the connector contact with the desired circuit becomes more difficult. Unfortunately, this difficulty is aggravated as the number of circuits is increased and their proximity to each other is decreased. Presently, it is not uncommon for printed circuit boards to be printed with different circuits as close to each other as fifty thousandths (0.050) of an inch from some center to center printed circuits, however, are being manufactured where the distance between centers is on the order of twenty-five thousandths (0.025) of an inch. Nevertheless, a twenty-five thousandths-inch spacing between the centers of electrical contact points can present very profound problems when there are as many as one hundred (100) or two hundred (200) circuits involved. Further, there are increased difficulties in manufacturing connectors as they are made smaller and smaller to accommodate the smaller more closely positioned printed circuits.
One proposed solution has been to provide a housing module which precisely spaces the connectors and combines them into a unit. Such a housing is also keyed with the circuit board to accurately position the connector against the proper circuit on the circuit board. To do this, however, requires precision manufacturing and, consequently, involves increased costs. U.S. Pat. No. 4,715,820 to Andrews, Jr. et al. is an example of such a device.
Another solution to the registration problem is provided by the so-called elastomeric connectors. Typically, such connectors consist of carbon impregnated layers of silicone which are separated by nonconductive silicone layers. The elastomeric connectors typically have very many layers which are arranged in a side-by-side relationship and which can each be as narrow as approximately two thousandths (0.002) of an inch. Thus, they alleviate the registration problem by providing a plurality of possible electrical connections for each printed circuit pad, even though these pads may be separated from one another by as little as twenty-five thousandths (0.025) of an inch. Elastomeric connectors, however, are bound together in a matrix so that the deflection of a conductive layer is directly affected by the position of its adjacent layers. Thus, depending on irregularities in the pads of the printed circuit boards, it can happen that conductive layers are held off their intended mating pads by surrounding higher pads. Further, elastomeric connectors are typically flexible and will, therefore, not reliably develop the higher contact pressures which are needed to insure a proper electrical connection. Stated differently, elastomeric connectors do not reliably establish low interfacial resistance. Accordingly, their utility for logic circuits can be questionable. An example of an elastomeric connector is the product manufactured by PCK Elastomerics, Inc. and known commercially as "Carbon Stax".
The present invention recognizes that a connector can be manufactured which develops the pressure between contact and printed circuit pad required to insure low interfacial resistance, but which does not require keyed registration to insure proper connection between the various electronic components. The present invention also recognizes that metallic contacts can be effectively juxtaposed to provide a high contact density connector without compounding machine tolerance errors.
In light of the above, it is an object of the present invention to provide a high density stacked electrical connector which establishes a good electrical contact between connected electrical components for high density current flow. Yet another object of the present invention is to provide a high density stacked electrical connector which has low interfacial resistance between the connected electrical components. Still another object of the present invention is to provide a high density stacked electrical connector which provides a reliable and predictable means for achieving proper registration between the connected electrical components. Another object of the present invention is to provide a high density stacked electrical connector which obviates the tolerance problems typically associated when aligning a printed circuit board with the connector. Yet another object of the present invention is to provide a high density stacked electrical connector which is rugged and establishes a robust connection for electrical components. Still another object of the present invention is to provide a high density stacked electrical connector which is relatively easy to manufacture and comparatively cost-effective.